1 Technical Field of the Invention
The present invention relates generally to a stator for an electric rotating machine designed to ensure effective dissipation of heat from a stator coil.
2 Background Art
Stators for use in electric rotating machines are known which are equipped with a hollow cylindrical stator core in which a plurality of slots are arrayed in a circumferential direction thereof and a stator coil which is made up of a plurality of conductor wires wound through the slots of the stator core.
Japanese Patent First Publication No. 2009-195004 teaches the above type of a stator coil which is formed by multi-phase windings (e.g., a U-phase winding, a V-phase winding, and a W-phase winding) made by conductor wires disposed in slots of a stator core. In order to improve the packing factor of the conductor wires, the conductor wires are each designed to be rectangular in cross section traversing a length of the conductor wires. Additionally, each of the multi-phase windings is bent in the form of a crank when developed. The phase windings are wound several times and spiraled into a hollow cylindrical form.
The conductor wires include in-slot portions which are arrayed in each of the slots in a radial direction of the stator core and square in transverse cross section thereof. The in-slot portions are, as illustrated in FIG. 12, arranged within each of the slots close to each other in order to increase the packing factor thereof. Specifically, entire surfaces of adjacent two of the in-slot portions which face one another in the radial direction of the stator core are placed in contact with each other.
The stator of the electric rotating machine usually has the problem that heat generated by the stator coil results in a deterioration in magnetic property thereof. The heat is transmitted from the stator coil to the stator core and then released or dissipated. If however, a sufficient quantity of heat is not dissipated, it will cause the temperature of the stator coil itself to rise, thus resulting in an increase in electric resistance of the conductor wires of the stator coil. This also gives rise to heating of the conductor wires.
In the layout of the in-slot portions in FIG. 12, the entire surfaces of adjacent two of the in-slot portions are in close contact with each other or abut each other through a little gap, thereby leading to increased difficulty in transmission of the heat from the in-slot portions to the stator core.